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Technology & equipment 2 min read

Solar Panel Types: Mono, Poly, Bifacial, TOPCon and HJT — Which Is Best?

A simple guide to the panel technologies available in 2026, how they differ in efficiency, heat performance and lifespan, and when bifacial makes sense.

GPS Engineering Team
Solar Panel Types: Mono, Poly, Bifacial, TOPCon and HJT — Which Is Best?

Quotations are full of terms like Mono PERC, TOPCon and bifacial. These aren’t marketing details: they genuinely affect plant output over 25 years, especially in Egypt’s heat.

Key takeaways

  • Monocrystalline panels are today’s standard; polycrystalline is now rare.
  • TOPCon is the most widespread technology in 2026, with efficiency above 22%.
  • Bifacial panels add yield from light reflected off bright roofs and ground.
  • Heat performance (temperature coefficient) matters a lot in Egypt’s climate.

Technology comparison

Technology Approx. efficiency Heat performance Notes
Poly 16%–18% Weak Legacy technology
Mono PERC 20%–21.5% Good The standard until 2023
TOPCon (N-type) 22%–23.5% Very good Most widespread today
HJT 22.5%–24% Excellent Slightly pricier
Back-contact 23%–24.5% Excellent Highest efficiency for tight spaces

Why the temperature coefficient matters

Panel ratings are measured at 25 °C, but cell temperatures on an Aswan roof in summer can exceed 65 °C. Every degree above 25 trims output slightly:

-0.35%per °C, approx., PERC
-0.29%per °C, approx., TOPCon
-0.25%per °C, approx., HJT

The gap looks small, but over a summer — and 25 years — it adds up to thousands of extra kWh. Read how heat affects panels.

Bifacial panels

They capture light on both faces. The rear side benefits from light reflected by the ground or roof, which can add 5%–15% on white roofs, pale sand or raised ground-mount arrays. On metal roofs very close to the panels the gain is limited.

What about panel wattage?

Today’s panels range from 550 to 720 W. Bigger panels reduce connections and structure, but are heavier and larger, so we choose the size that suits the roof and mounting method.

How to check panel quality

  • Certifications: IEC 61215 and IEC 61730, plus IEC 61701 for coastal sites.
  • Product warranty (12–15 years) and performance warranty (25–30 years).
  • Annual degradation (ideally 0.4% or less for N-type).

How much would your plant save?

Get system size, cost and expected savings in under a minute.

Open the calculator

#Bifacial#TOPCon#ألواح

GPS

GPS Engineering Team

GPS engineers have designed and built solar plants across Egypt for 15+ years. Here they share what they learn in the field.

Frequently asked questions

Are more expensive panels always better?

Not always. What matters is the cost per kWh produced over the plant's life, plus the manufacturer's quality and warranties.

Can different panel types be mixed in one plant?

Avoid mixing them on the same string. Different types can sit on separate MPPT inputs of the inverter.

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